Figure 1

Theoretical prediction of synaptic modification as a function of the initial synaptic strengths in the absence of a frequency mismatch. The colors show the stable fixed point of the time lag Δt^* = χ^*/(2πν) of spiking of the neurons given by Eq. (9) and the vector field shows the direction of the change of the synaptic strengths from Eq. (3). The yellow solid curves denote the simulated synaptic evolution for three different initial values. In each row, the firing frequency ν is constant, but it increases from top to bottom in each column. Based on the initial synaptic coupling, different attractors may be achieved: Bidirectional/unidirectional (left column), unidirectional (middle column), and decoupled/unidirectional (right column) state. The dendritic propagation delay is \({\tau }_{{\rm{d}}}=0.5\,\,{\rm{ms}}\) and the axonal delay is denoted above each panel. STDP parameters are A₊ = A₋ = 0.005 and τ₊ = τ₋ = 20 ms.